Differential microphone-transmitter.



J. J. GOMER.

DIFFERENTIAL MICROPHONE TRANSMITTER.

APPLICATION FILED OUT. 24', 1910.

Patented July 23, 1912.

2 SHEETS-SHEET 1.

Patented July 23, 1912.

2 SHEETS SHEET 2.

plex form ofdifferential transmitter in have invented a certain provement transmitters.

JOHN J.) comma, OECHICAGO, ILLINOIS,

JAISSIGNOB To AUTOMATIC ENUN'CIATOR COMPANjZ, .OF-ZCHICAGO,ILLINOIS,--.A CGBBOBATION OEILLINOIS;

' IJIFEERENTIA .monornonnmmsmrrnn.

fipeci'fication'of Letters Patent.

Patented July 23, 1912.

Application filed 0ctober'24,--1 910. serial ml. 588,789.

'1? all whom if my concern:

Be it known that I, citizen of the United States of America, and resident of Chicago, Cook county, Illinois,

new and useful Imin :Diiferential vMicrophone- Transmitters, of which the following-is a specification. a

My invention relates to transmitters of the kind ordinarily known as differential In the simple form of transmitter ,of this kind the resistance is variedyonly at one point in the circuit, or at one point in each circuit, as the case. may be, as by the use ofa single electrode between two other electrodes' There is, however, a more comwhich the resistance is varied at a plurality of points in thecircu t, or meach circuit,

and in which a plurality of stationary elec-- a plurality of movable trodes alternate with electrodes. It is to this form of diflerential y transmitter that my invention more particularly relates. 4

Generally stated, the object of my invention is, therefore, to provide an improved and highly eflicient differentialtransmitter" of that kind in which a plurality, of elec-, trodes are disposed between and alternately with a plurality of other electrodes.

A special object is to provide a trans mitter of this type inwhich the construction is more simple. and free from certain compllcations than those heretofore em ployed or propose'd'of similar character...

' 1 is a longitudinal section of a transmitter Another object is to provide an improved construction and arrangement whereby a To these and other useful ends, my'invene tion consists in matters hereinafter more fully set forth and claimed. e

In the accompanying drawings :'F1gure embodying theprinciples of my invention. Fig. 2'is "a rear view of the microphone and the disk to which the said microphon i's' connected bya bridge. Fig.3 isa sectional] JOHN J. Comm, a.

plurality of stationary electrodes are dis posed between and alternately with a plus view 101: the different parts separated. Figs. 4, 5 and 6 are views similar to those pre- "iously: described; showing a slightly ditferfrontplate A provided'with a shoulder a on theinside thereof, and with an internal,

screw th-readedportion a. It is also provided with a central opening a for the usual mouth piece B. The diaphragm C is seated against the shoulder a, but insulated therefrom, as shown, and is clamped in place by a disk D and ring E that engages the threaded portion a of the front plate, the said disk and ring being ins'ulatedfrom each other, and the disk being insulated from the front plate, but not from the diaphragnnthe latter being in electrical contact therewith. This disk D has a central-aperture rl for the microphone F Which is carried directly on the back of the diaphragm. Another microphone'G is secured't'o the front of the saiddiaphragm. The microphone F consists of a metal cup f,

a threaded clamping.

front and back movable electrodes f and f a stationary or middle electrode f and mica insulating pieces j, and f, together with the usual filling f of granular carbon. The said insulation 7" insulates the granular carbon from the metal cup and the mica F insulates the electrode f from the said cup and diaphragm. The parts F, f and f are secured together by the hollow rivet f and a similar rivet f secures the electrode f to the-back of the diaphragm. The microphone G- is similarly constructed and comprises the metal cup 9 and the front and back electrodes g' -and 9 together with the middle or intermediate electrode 9 and the granular carbon'filling 'g, 'It also comprises the ring insulation and the flat 'insulating pieces' g a'nd'g The front electrode g and the'insulations 9 and g". are clamped to .the endwall of the cup 9 by the hollow rivet g". Y The two cups f. and g' have their open'ends clamped upon opposite sides of the diaphragm'by the rivets 9. The electrodes f and g are-electrically secured to the stem H, which extends through the rivets f and 'j", and which is adjustably secured. to the bridge :I onthe disk D, the" said-'bridge and diskbeing insulated from each other. One .Lcircuit who goes to the disk 1),toconnectfwith electrodes f' and g another wire goes to the electrode f and a third wire goes to the electrode 9'; but the electrodes f and g are not connected directly with any circuit connections, the granular carbon being the only medium by which current can pass tool from these two stationary electrodes. The circuits may be of any suitable character. Fluffy asbestos is employed for filling the said hollow rivets after the parts have been assembled andthe granular carbon introduced through the passages of said rivets. I

In Figs. t to 6, inclusive, the construction is substantially the same as that previously described. The only difference, in fact, is

that in this casethe microphone boxes J and K have their closed ends secured to the diaphragm, and have their open ends closed by the caps j and'k. Otherwise the two transmitters are'the same, as each involves two difi'erential microphones, each microphone comprising a pair of movable electrodes and a stationary electrode. 1

A differential microphone transmitter of this kind is, I find, particularly; adapted for y use in loud speaking systems using heavy currents and requiring clear enunciation and pure tone. The microphones are so constructed, it will be observed, that they can be operated at the high temperatures which frequently result from the use of heavy currents for loud spcakingfpurposes. The mica insulation-protects the structure when the carbon becomes, highly heated.

lVhat I claim as my invention is:

1. In a transmitter, a diaphragm, a plurality of electrodes movable with said diaphragm, a plurality of stationary electrodes alternating with said movable electrodes,

and a receptacle containing granular car- 'bon, which carbon is between said electrodes, said receptacle being movable with said diaphragm.

2. In a transmitter, a diaphragmpa carbon receptacle and a plurality of electrodes movable with said diaphragm, a plurality .ofstationary electrodes alternating with said movable electrodes, granular carbon contamed 1n said. receptacle between sald electrodes, and means mslde of the transmitter for electrically and mechanically connecting the said stationary electrodes together.

Copies of this patent may be obtained for -mentioned diaphragm.

4. In a transmitter, a diaphragm, a differential 'microphone on the back of said diaphragm, a differential microphone on the front of said diaphragm, a support, and a connection from the said support to the inside of saidmicrophones.

5. In a transmitter, a diaphragm, a stationary electrode in front of said diaphragm, a stationary electrode back of said diaphragm, and connected withsaid firstelectrode, Variable resistance means cooperating with said electrodes, a bridge back of said diaphragm, and a connection from said bridge .to said stationary electrodes.

6. In a transmitter, a diaphragm, a plurality of electrodes, a filling of granular carbon between said electrodes, and a stem rigidly connecting together a plurality of said electrodes, which stem also serves as an electrical connection between said electrodes.

7. In a transmitter, a diaphragm, a difier ential microphone on the back of said diaphragm, a differential microphone on the front of said diaphragm, a disk and clamping ring for holding the diaphragm in place, a bridge on the disk, and an adjustable connection from the bridge to said microphones.

trical connection between said microphones,

9. In a transmitter, a diaphragm, differential microphones disposed at opposite sides of said diaphragm, and a connect1on between said microphones extending through said diaphragm, WlllCll connection electr1-' cally connects, one microphone with the other.

Signed by me at Chicago, Illinois, this 12th day of October, 1910.

JOHN J. COMER.

\Vitnesses:

M. Bi Dunmoiv, E, H. Cuzco.

five cents each, by addressing the Commissioner of Patents, -Washington, ID. 0. 

